Telephone system



July 7, 1931. R. TAYLOR ET AL TELEPHONE SYSTEM Filed July 24, 1929 Im-Z-m maid T Re 1 Lam-1213 Mair m s fnpsun Patented July 7, 1931 )UNITEDL'STATES PATENT OFFICE TAYLOR, OF LIVERPOOL, AND LANCELOT MARTIN SIMPSON, F T'HORNER, I NEAR LEEDSQEN GLAND, ASSIGNORS T0 ASSOCIATED TELEPHONE AND TELEGRAPH COMPANY, OF GHIGAGQVILLINOIS, A CORPORATION OF DELAWARE TELEPHONE SYSTEM Application filed July 24, 1929, Seriallo. 380,718, and in Great Britain July 26, 1928.

The present invention relates to telephone systems and is more particularly concerned with arrangements for automatically obtaining access to what are known as private branch exchanges which are generally provided for subscribers having more than one exchange line. In such cases it is usually desirable that the subscriber in question should be given a single number corresponding to the first line of the private branch exchange and that if thisline is busy the automatic switch serving to connect therewith should hunt automatically to find an idle one of such lines. When switches of the well-known two-motion type are employed having ten contacts in a level, difliculties arise if there are more than ten lines leading to a particular P. X., since for giving serviceof the klnd; 7 indicated above it is necessary for the switch to hunt' over more: than one level.

One of two methods has been employed hitherto for handling this problem when using switches of the type mentioned. In accordance with one method special contacts are provided in connection with groupbusying arrangements so that if all the lines accessible from one level are busy the switch is automatically moved past'that level owing to busy potential picked up from the special contact and hunting then takes place in the succeeding'level if this includes an idle line. Ac-

cording to the other method the switch actually tests each contact in turn, the switch wipers moving ifnecessary over all the contacts in one level and then being returned to the beginning of the level, stepped up one step, and started hunting in the new level,'the

process being repeated if necessitated by the size of the group. The present invention is particularly concerned with the provision of a new and improved switch for handling trafiic to P. B. X.s with a large number of lines according to this latter method.

. According to one feature of the invention in a two-directional automatic switch adapted-to hunt automatically over a plurality of levels in turn a relay energized due to the switch wipers being moved clear of the banks isadapted to complete the circuit, of the vertica-l magnet.

adapted to hunt automatically over a plurality of levels in turn the relay which completes a circuit for the release magnet after all the contacts of a; level have been tested is adapted to lock up dependent upon normally closed springs controlled byv the vertical magnet.

A further feature of the invention is that in an automatic switch adapted to hunt automatically over a group of lines the hunting operation is initiated due to special potential picked up by a control wiper and is dependent for its maintenance on a difl'erent potential picked up by the same wiper.

The invention will be better understood fromthe following description of one method of carrying it into effect which should be taken in conjunction with the accompanying drawing. It will be understood however that the invention is not limited to the exact circuit details shown and that various modifications could be made by those skilled in the art without departing from the spirit of the lnvention.

Referring now to the drawing, this shows a circuit diagram of a P. B. X. connector of the vertical and rotary type arranged to hunt if necessary over a plurality of levels. In order that the operation may be fully understood a description will first be given of the setting up of a call to an individual line. In the case of such a line the contact engaged by wiper will be left dead so that no circuit will be completed for causing the switch to hunt.

When the connector is taken into use from the preceding selector, a circuit is completed over line conductors 61 and 62 for line relay A which thereupon operates and at armature 1 completes a circuit for release relay B which operates also and at armature 10 applies earth to release trunk conductor 63 to guard the connector and hold up the preceding switches, this operation being efi'ected as usual before the slow relay supplying guarding earth in the preceding switch has released. Relay B moreover at armature 6 prepares a circuit :for relay H, at armature 7 opens a point injthe circuit of the release magnet'Z and preparestheimpu'lsing circuit, at armature 8 prepares a number of operating and holding circuits and at armature 9 connects earth by Way of-back contact and armature 29 to the lower winding of relay A to replace that Which will be removed at off-normal .springs58 as soon as the switch goes offner 'inal. No further changes take pla'ceuntil- I th'e nefit series of 'ini'pulsesis transmitted whereupon relay A dc-energizes. intermittently in accordance With the value of the; digit sent; Upon each de-energizatlon of relay A a circuitis completed as follows: ear th,-

, armaturej'l and-its back contact, armature 7 andits'front contact, armature 28 and its back contact, armature 49 and its back con-1 tact, and thence vby ay of armature 22- and; itsback' contact, WlIlCllIlg of vertical magnet Vto battery and also over back contact and V armature 37 and upper Winding of relay G to 7 battery; Theverticalmagnet operatesinresponse to each impulse and raises-the shaft,

and Wipers a corresponding number of steps. Relay C also energizes and at armature 13 short-circuits its lower Winding thereby making itself slow to release so that it'holds up throughout the tr'ainlof impulses. 1At arma- 1 v turell it .prepares'a circuit for relayzG, at

armature 12 removes the SllOIt-ClI'CLlltftOnl:

around resistance 42, at. armature 14' shorti;

- circuits armature 30and at armature 15v prepares-acircuitjfonrelay At the end; of the train of impulses relay C releas'es-and a circuit is then completed torrelay E as fol-T armature 74 8 111 141, its. back Contact, "back icon tact and armature 13, off-normal springs-57 armatu re and its back contact; Winding of relay E to battery.,1elay 'E'thereupon atarmatures 16 and 23 disconnects relayl? and fswitche s'the speaking leads-through, but this operationis witli'olltfefiectiat the present time, Belay E also at armature 17 closes a pointin the circuit of the supervisory lamp j 1 USE, at armature 18 completes a locking cir- V cult for itself independent of armature 13 atarmature 19 opens a point inj the busy flash-circuit, at'armature20 applies an addi tional eartlito'the---lower Winding of frjel A, atfarmature. 21 closes a:-point iii-the circuit of relay HS and at armature 22(cennecte up the rotary magnet lt in place ofthe vertical magnet V.- The final series ofimpulscs-is now sentin and the rotary/magnet R is. according-1y operated to --rotate the -Wipers correspondingnumber of steps. Relay- C is I again." energized and remains energized:

throughout theseries of'impulses; In case- -the switch Wipers should pass overbusy lines during the rotary motion wiper 5:4 will pick 7 up earth Which Wll'l be extended over frontcontact and armature 6, armature 11 audits? front contact and resistance 42 toitheiupper'j winding of relay G. Owing to'the-inclusion of resistance 42 in 'its circuit, relay at this time only operates its lightfarmature 26 thereby preparing a-locking circuit for itself and openlng the circuit of relay H.

In case the Wanted line is time, relay GWill be operated when the ipers come to rest and upon the ole-energization of relay C resistance42 Will beshort;

circuitedi Relay G then -operates-ful l y-and at armature 2? places a'ii urther short-circuit round resistance 42, at armature 28"prepares therbusyshold circuit for relay B over conductor 59, at armature29 prepares the conbusyat this i nection of busy tone and busy .fiashbattery over lead 60 tothe' lower Winding of relay A at. armature 30--opens the circuit-of relay superimposed busy'tonezare alternately con nected to, conductor 60 and battery :is'conn'eet ed to conductor 59'during' the same interval; that battery 'iscconnected to conductor- Upon-the: d'eenergization of relay Eyafter fa shortinterval the busysignal is' transmitted 7 back to the calling part. In the case of a call originating at a subscribersstation, the bus-y tone. oil-conductor 6 0, above referred to, will 1 constitutethebusy signal;- In acall originating'. at'ga'nianualswitchboard; the supervisory lamp of the calling cordy'vill flash'dueto'the intermittent: application of battery to trunk conductor -62j via the lower Winding of 'relay i A and conductor 60. {Relay A will'deenen' g'ize with each battery pulseand Lat armature L Wfillcomplete aholding circuit for'the u-pr er Winding of relayvB'by Way ofzarmatures' Z- and 28" and conductor 59. The calling party,-;if a" subscriber, will replace hisreceiver or, if arr-operator, Will withdraw the plug of the'callirig cord from the jack. Thisopens theicircui't of 'relay A which in turn brings downrelay B, "whereupon a circuit is i com pleted for" release magnet Z 'oyer- :armature's '1 and-7 and their back'contactsandiolfmor mal springs 56. Magnet Z accordingly -operates, tojirestore theswitch to normal in the usual manner and at its armature 2applies earth'to; release'trunk conductor '63Jso as to ensure that'the switch shall not'becoine um guarded "before it is .:completely ream-ea 'Thelocking. circuit of'rel'ay is opened 'on the de-energizationof relay B. V

Consider now the casein which the anted partyslineis idle whenit is connected with: in this case wiper 54 Willnot find earth at the end of the rotary movement and relay G Will therefore. not be operatedLJ ;Acircuit is now completed from earth"; 'frontcontact and ar mature 2 3, armature 26 and its backfcontact, lower Wmding-of relay H, back Contact? and armature 11, armatureti and its front contact, wiper 54 and byway of the test contact of the wanted line through/the cut-off relay and magnet of the called partys line switch I to battery. The cut-off relay operates in this circuit to clear the called line of its normal battery and earth connections and relay H also operates and at armature 47 completes a locking. circuit for itself over its upper winding. Moreover at armatures 44 and 51 it connects up wipers 52and 53, at armature 45 completes a circuit over which the calling party hears ring-back tone, at armature 46 completes the circuit of the supervisory lamp CSH, at armature 48 applies direct earth to the test wiper 54 at the same time opening the circuit of relay E, at armature 49 opens a point in the impulsing circuit and at armature 50 connects up the lower winding of back bridge relay D, this relay having previously been disconnected to prevent any tendency to chatter due to condenser kicks during dialling. Relay E is slightly slow to release and this short delay period ensures that the cut-off relay shall be operated fully before ringing current is applied to the wanted line, thus obviating the danger of premature tripping. When relay E falls away the circuit of lamp CSH is opened and at armatures 16 and 23 ringing'current is connected up through the upper winding of the ringing trip relay F. The wanted partys bell is therefore rung in the usual manner, and when he. replies by removing 'his receiver, a direct current bridge" is completed across the line so as to operate relay F. Relay F thereupon at armature 25; locks up overits lower winding in series with, relay E via ofl"normal contacts 57 and armature 30 and its back contact. Relay E is again operated to cut off the ringing current and complete the talking circuit at armatures 16 and 23. Back bridge relay D is now operated over the called partys loop and at armatures 4 and 5 reverses the connections of line relay A to conductors 61 and 62 for metering or similar pur poses. The two subscribers may new converse, battery feed being supplied from relays A and D to the calling and called parties respectively. At the end of the conversation both subscribers will replace their receivers. Assuming that the called party replaces his receiver first, back bridge relay D will deenergize and at armature 3 will complete a circuit for the supervisory lamp GSH. Continued lighting of this lamp will thus give an indication that the called subscriber is being held owing tothe calling subscriber having omitted to replacehis receiver, and

a an attendant can then take the necessary steps to prevent the called partys line being tied up. When the calling'party replaces his receiver relays A and B de-energize and the release of the connection takes place in the manner previously described.

Consider now the case in which the called party has several lines, so that if the first line is busy the connector must hunt automatically for a free line. It should be explained that the contacts engaged by wiper 55 are so connected that the first line of a P. B. X. group has battery connected thereto, intermediate lines have these contacts strapped to the ordinary test cont-acts, while for the last line the contact is left dead. Suppose, therefore, that in response to the dialling of the directory number of the wanted party the wipers of the connector have been operated into engagement with the first line of a P. B. X. group; If this line is idle, switching through will take place immediately in the manner above described. It the line is busy, relay G will be operated as previously described, and accordingly while relay E holds up after relay C is Clo-energized a circuit is completed for relay HS from battery picked up by wiper 55, armature 31 and its front contact, hack contact and armature 38, armature 15 and its back contact, front contact and armature 21, lower winding of relay HS, armature 8 and its front contact to earth. Relay HS therefore operates and at armature 34 completes a circuit for rotary magnet R so that wipers 52-55 are advanced a further step, while a circuit is also completed for relay C and this again operates and again completes a circuit for relay E so that this relay does not de-energize. The operation of relay C opens the initial energizing circuit of relay HS but this relay is locked up by way of its upper winding over the rotary interrupter springs 24 and also relay G is n'iaintained over its lower winding and back contact of armature 36. When the wipers are properly centered on the next set of contacts, interrupter springs 24 open. and thus interrupt the circuit of relay HS. If this set of contacts is idle, relay Gr de-energizes and switching through takes-place, nit assuming that the set of contacts now engaged by the wipers is busy, earth will be picked up by both wipers 54 and 55, and this will prevent relay G from deenergizing. Moreover the earth on wiper 55 will cause the operation of relay HS over its upper winding and front Contact of armature 15, Consequently relay HS at armature 34 again completes a circuit for the rotary magnet and the stepping operation is repeated. This cycle of operations continues until an idle line is encountered or the last line of the group is reached and found to be busy. In this event since the contact engaged by wiper 55 now dead, relay HS will be unable to re energ'ize and relay G will be maintained from the earth picked up by wiper 54 and will effect the transmission of the busy signal in the manner described above.

Suppose now that the group of P. B. X.

lines inquestion'extends over more than one level and that the switch tests all the lines 'infthei'first'level' and finds themall busy:

' Since the tenth set of'cont-acts in the level his not associated with the last line iofthe group, the contacts engaged by wipers 54s and" 55 will be strappedtoge'ther and thus the switch will be caused to take a further. step into the eleventh rotaryposition; In this p- 1' 7 sition the cam springs S are operated whereupon a circuit is completed for relay HG which; at armature opens its energizing circuit and; locks itself up dependent upon the vertical interrupter springs .33. I 1 110 also at armature 41 completes a clrcult for the release magnet Z, at armatures 36 and 39 prepares a circuit for the verticalmagnet V including theresistance 43,. at armat ure-38 opens a point in the-circuit of relay HS to prevent this relay re-energizing for the pres ent and at armature 37 completes a circuit for relay G which is therefore operated in the usualgmanner. Owing to the operation of release magnet Z the switch will commence slightly slow to release so that the wipers shall lifl'l be free from vibration before an attemptis made to cutin on the next level. When relay HG has released, a circuit is again completed for relay HS as follows: battery, upper wind ing of relay'I-IS, rotary interrupter springs 2 back contact and armature 36, armature 32 and its front contact, rotary off-normal springs NRarmature 8 and its front contact to earth. Relay HS therefore at armature .84 completes the usual circuit for the rotary BGEmagnet, thus causing the-wipersto cutin-on thelevelnow reached. Thereafter automatic hunting takes place in the manner previously described until a freeline is'rcached or the last line f of the group. Clearly should the group be of such size to warrant it the autO- matic vertical step couldbe repeated so as to causethe switch to hunt also over the succeed ing level. Clearly also if a group terminates v onthe last contact of alevel the fact that Goithefourth contact is'i'n this case left dead will prevent the wipers moving to the eleventh position and thus starting hunting on the sue ceeding level. 7 It will be seen moreover that, if'an intermediate number dialled in the e 'firstplace as' may, be desirable for night operate inthe usual way #tolseize the line.

Relay When the connector to position the wipers for 'hunt-'= ing over a differentlevel, and a circuit includ servicethe Swath will not l unt a m' -rat i busy. but'willat l once return the busy signal to the callingxparty."- Theloper'ation under these conditions will bethefsameasthatpre viously described" for a' call toan individual 7 line. VVhilethe'contacts engaged by wipers 54s. and 55 will be strapped in'this caseythis will be without effect. If the intermediate line is-idle when connected'with, relay lwill 7E If'the line is busy, wipersffi l and' '55"will=b'oth' encounter earth and relay will operate as usual following the releaseofjr'elayCQ Under'these conditions the previously described circuit for the lowerjwinding of relay will be prepared but since'wiper55 is earthed the'relay cannot operate to initiate furtherrotation ofthe wipers. Theconnector therefore returns a busy signal to the calling party as in previously described connections.

Preferably the rotary 'ofi-normal' springs and the cam springsare built up in a single unit and are arranged to beioperated' by the same member in dilferent positions for in stance as shown in the British Patent" No.

321,985, granted Feb.,1s, 930: This; -arrangement economizes mounting space and is 7 found tozbe entirely satisfactory, as -regard its operation. g According to the: invention; therefore it' is possible to arrange for a-switch'identical" in mechanical construction with the standard two-motion switch to hunt successively over; a number of levels in searchwoffan idle line, the switch being released when a coir'qoletef level has been dealt'with 'a'nd the vertical magnet coming into operationas soon'asfthe' rotary portion of the release has been eflected. What we claim as new and desire to secure by Letters Patent is,: j I g 1. In a two-directional multi level switch, wipers, means for positioning: said wiperson a particular level,fmeans" for automatically moving said wipers over the level insearch of an idle set of contacts, contacts operated mechanically responsive to the movement ofthe wipers past the lastset of' fcontacts in the level,-' a relay for causing the wipers to be automatically positioned on another level; and acircuit including said cont acts "for opcrating said relay. 5 r i [I'- 2. In twodirectional switch adapted to hunt automatically over a plurality *of'level's" for an idle truck, WlPQI S EL' shaft-carrying said wipers, a cam on saidsha'ft, contact sop erated by said cam when the wipers are moved past the last trunk" accessible ina level' inl which all trunks have bee n tested and round; busy, a relay for controlling the operat'ion'of ing said contacts for operating said relay. g

3. In aswitch equipped with primary and secondary. stepping magnets and having ac- I cess via a set of wipers totrunks in a' plu-ri 1 0 i'ality of levels, means for directively operating the magnets to position the wipers on a particular level, means for further operating the secondary magnet to advance the wipers over the level in search of an idle trunk, contacts operated responsive to the wipers moving past the last trunk accessible in the level, a relay for controlling the re operation of the primary magnet to position the wipers for hunting over a different level, an operating circuit for said relay including said contacts, and a locking circuit for said relay including contacts controlled by the primary magnet.

4;. In a switch having a directive and an automatic primary movement and a directive and an automatic secondary movement, a control wiper, means for directively operating the switch in its primary movement and in its secondary movement successively, means effective when said wiper encounters a particular potential at the completion of the directive secondary movement of the switch 'for automatically operating the switch in its secondary movement, means thereafter effective responsive to said wiper encountering a different potential for continuing the secondary movement, and means responsive to the switch reaching the limit of its secondary movement for automatically operating the switch in its primary movement.

.5. In a telephone system, a switch having a directive and an automatic primary movement and a directive and an automatic secondary movement, a control wiper and a test wiper, contacts adapted to be engaged by said wipers, a battery, means for directively operating the switch in its primary movement and in its secondary movement successively, means in the switch efiective when said control wiper engages a contact connected to one pole of said battery and said test wiper engages a contact connected to the other pole of said battery at the completion of the directive secondary movement of the in its secondary movement, means in the switch thereafter effective responsive to both said'wipers engaging contacts connected to the other pole of said battery for continuing the secondary movement, and means in the switch responsive to the switch reaching the limit of its secondary movement for automatically operating the switch in its primary movement.

6. In a switch having a directive and an automatic primary movement and a directive and an automatic secondary movement, means for operating the switch in its primary movement and in its secondary movement successively, a double wound relay for controlling the automatic secondary opera tion of the switch, a control wiper, a circuit for operating said relay over one winding completed responsive to the control wiper encountering a particular potential at the completion of the directive secondary movement of theswitch, a circuit thereafter effective for operating said relay over its other winding responsive to said wiper encountering a different potential, and means responsive to the switch reaching the limit of its secondary movement for automatically operating the switchin its primary movement.

"Z. Ina multilevel switch, vertical and rotary stepping magnets, wipers, means for operating the magnets to position the wipers on a particular level, automatic means for further operating the rotary magnet to move the wipers over the level in search of an idle trunk, contacts closed responsive to the wipers reaching the limit of their rotary movement, a relay operated over a circuit including said contacts, means controlled by said relay for restoring the wipers to their vertically operated position, other contacts closedresponsive to the wipers reaching said position, ianda circuit including said other contacts for operating the vertical magnet to move said'wipers to a different level.

8-. In a telephone system, an automatic switch equipped with wipers, means for positioning thewipers on a level of contacts, automatic means for moving the wipers over the level in search of an idle set of contacts and to a position beyond the last set of contacts in the level when all contact sets are busy, spring contacts closed when the wipers are advanced to a position beyond the last set of contacts in the level and opened when the wipers return to the last set of contacts in the level on restoring to normal position, a release magnet for controlling the restoration of the wipers, and a circuit including said spring contacts for operating said magnet.

9. In a connector switch, a test relay, a test wiper, a circuit for partially energizing the relay responsive to the test wiper engaging a. busy contact, contacts on said relay closed responsive to the partial energization thereof, a circuit including said relay contacts for fully energizing said relay, and a busy signalling circuit closed by said relay when fully energized.

10. In a-connector switch, a relay energized during the setting of the switch, a test relay, atest wiper, a circuit completed by said first relay when energized for partially energizing said test relay responsive to said test wiper energizing a busy contact, and a circuit completed responsive to the deenergization of said first relay and the partial energization of said test relay for fully energizing the test relay.

11. In-a connector switch, a relay energized during the setting of the switch, a test relay, a circuit completed by said first relay when energized for partially energizing said testrelay responsive to the switch connecting with a busy line, a circuit prepared by the 5 forcompleting said last circuit.

12: Ina connector switch, a slo'w-to-release relay energized during the setting of the switch and released a short interval after'the -setting operation iscompleted, a test relay, a

1 test Wiper, means controlled by said first re lay for connecting said'test relay to said test wiper, meansqfor partially. energizing said test'relay overfacircuit including said test 7 wiper, during the interval said first relay is energized; and means for fully energizing saielvtestzrelay overacircuit excluding said 1 jtest iper responsive to the deenergizati-on of said first relay. i 13. In anonnector switch, a relayenergized during the setting of the switch, a testrelay,

a resistance, means controlled by said first relay forpcompleting acircuit for said test relay andqsaidfresistance in series WhE/IBbY' said testrelay is partially -energized,' and Z5 meansvcontrolled by said first relay, on d'e= energizing. at the completion of the, setting k operation for. short-=circuitingsai'd resistance Whe1'ebysaid test relay is fully energized. 7 Mi Ina connector-sWitcharelay energized di'lringthe setting of the switchand deenergiz'ed at the completion of the settinggoperation, a test relay a resistance, ,a' test 'vvip'er a circuit including. said resistance and vsaid 1V Wiper for partially energizing said testv relay i completed by said first relay whenenergi-zedg, contacts closed by said test relay when pa'rrti-ally'energizedyan-d acircuit inclu'diilgsaid H p I contacts .but: excluding said resistance and v I V v said Wiper for fully'energizing said test relay con1pleted by firstrelay when'dee'r er "gizecl -mv V r M a 15. In a rrnu'lti -leve'l switch, vertical and rotariy stepping niagnets, Wipers, a shaft-car rying said Wipers, acam on said shaft, means 7 i for operatingthemagnets to position the ivviggrers on a particular leveL'a'utomatic means 01 further operating the rotary magnet to move the Wipers over the level in searchof an idle: trunk, normally open contacts closed said cam responsive to the 'wipersme'aohing-the i V v i I limit of their rotary movement, arelay operated over a circuit including jsai d contacts, means controlled by said relay for restoring thewi pers to "their vertically operated position;,'rother contacts closed by said can; re-- sponsiv'e tojthe wipers returning to said igpos'i tion, and a circuit including said'other corrtacts ifor operating said vertical magnet 'to move the Wipers to ardifferent level.

c0; In testimonywhereof We have SlgI'IGd OiII' names at Liverpool, England,this 20th flayo'f June,1-929.' v

c o z LI-M. SIMPSQNQ. 

